MANILA (Reuters) - Philippine President Rodrigo Duterte said on Thursday he would issue an executive order for military support in his fight against illicit drugs, which he said was a national security threat and he would "kill more" people if he had to.

The mercurial leader ruled out declaring martial law and said he did not need extra powers, but wanted to bring the Armed Forces of the Philippines (AFP) into his drugs war because he could no longer trust law enforcement agencies.

All police operations in the drug crackdown were suspended on Monday due to deep-rooted corruption. Duterte has placed an anti-drugs agency in charge of the campaign and has said he wants the armed forces to play a supportive role.

"I still have to write the, whether it is a proclamation or an executive order, but I've taken in the AFP and raised the issue of drugs as a national security threat, so that I can call on the armed forces to assist," he said in a speech in Davao.

"I have limited warm bodies but so many wars to fight," he said.

The former city mayor said the police and the justice ministry-run National Bureau of Investigation could not be relied upon and promised "a cleansing, a purge".

Duterte did not say what the remit of the military would be in the drugs campaign, or give any indication of the number of troops that would be involved, but said they were necessary.

Some 7,600 people have been killed since Duterte launched his war on drugs seven months ago, more than 2,500 in what police say were shootouts during raids and sting operations.

The cause of the remainder of deaths remains disputed, with police blaming turf wars and vigilantism, and activists alleging widespread summary executions and police collusion with hit men.

New York-based Human Rights Watch said on Thursday involving the military was the wrong move because the armed forces had a track record of extrajudicial killings, particularly where Communist rebels were concerned.

"Using military personnel for civilian policing anywhere heightens the risk of unnecessary or excessive force and inappropriate military tactics," the rights group said.

"But there is also a deeply rooted culture of impunity for military abuses in the Philippines."

Duterte said he cared little for drug dealers and addicts and had underestimated the scale of the problem when he made his initial target of six months to win his war.

"You bleed for those son of a bitch. How many? 3,000? I will kill more if only to get rid of drugs and this campaign," he said. "I thought that would finish it in six months."